Diode-assisted gate turn-off thyristor

Abstract

A gate-controlled switch includes a gate turn-off thyristor in series with a diode. By using the diode in series with the GTO, the switch significantly increases the turn-off voltage that can be used for the current commutation. The unity turn-off gain and the snubberless turn-off capability are demonstrated.

What is claimed is:  
     
       1. A gate turn-off thyristor circuit having an anode and a cathode, comprising: 
       a gate turnoff thyristor connected to said anode;  
       a diode connected in series with said gate turn-off thyristor in a cathode current path and said cathode;  
       a turn-off voltage source connected to said diode; and  
       a gate loop stray inductance element connected between said turn-off voltage and said gate turn-off thyristor,  
       wherein a turn-off current commutating rate of said gate turn-off thyristor is based on a breakdown voltage of said diode.  
     
     
       2. The thyristor circuit of  claim 1 , wherein said diode is a discrete diode. 
     
     
       3. The thyristor circuit of  claim 1 , wherein said diode is a fast reverse recovery diode. 
     
     
       4. The thyristor circuit of  claim 1 , wherein a unity turn-off gain of said circuit is maintained by said diode until a turn-off transient process. 
     
     
       5. The thyristor circuit of  claim 1 , wherein the breakdown voltage of said diode allows said turn-off voltage source to have a turn-off voltage that ensures snubberless switching of said gate turn-off thyristor. 
     
     
       6. The thyristor circuit of  claim 5 , wherein said turn-off voltage V OFF  is selected to satisfy the following relation: BV E +BV GC >V OFF , wherein BV E  is the breakdown voltage of said diode and BV GC  is a gate-to-cathode breakdown voltage. 
     
     
       7. The thyristor circuit of  claim 5 , wherein the breakdown voltage of said diode BV E  is less than said turn-off voltage V OFF , so that a sum of a gate-to-cathode breakdown voltage BV GC /2 and the breakdown voltage of said diode BV E  is less than said turn-off voltage V OFF . 
     
     
       8. The thyristor circuit of  claim 1 , wherein a turn-off voltage V OFF  of said voltage source is of a level where current through an internal diode of the gate turn-off thyristor D GC  does not flow forward once commutated. 
     
     
       9. The thyristor circuit of  claim 1 , wherein said diode has a single diode die of a size equal to said gate turn-off thyristor. 
     
     
       10. The thyristor circuit of  claim 1 , wherein said diode is packaged inside a single press-pak with said gate turn-off thyristor. 
     
     
       11. A gate turn-off thyristor circuit having an anode and a cathode comprising: 
       a gate turn-off thyristor connected to said anode;  
       a plurality of parallel-connected diodes between said gate turn-off thyristor in a cathode current path and said cathode;  
       a turn-off voltage source connected to said plurality of diodes; and  
       a gate loop stray inductance element connected between said turn-off voltage and said gate turn-off thyristor;  
       wherein said plurality of diodes form a diode element having a breakdown voltage, and wherein a turn-off current commutating rate of said gate turn-off thyristor is based on the breakdown voltage of said diode element.  
     
     
       12. A method for performing snubberless switching of a gate turn-off thyristor circuit, said circuit including an anode and a cathode, comprising: 
       connecting a gate turn-off thyristor to said anode;  
       connecting a diode in series with said gate turn-off thyristor in a cathode current path and said cathode;  
       connecting a turn-off voltage source to said diode;  
       connecting a gate loop stray inductance element between said turn-off voltage and said gate turn-off thyristor; and  
       increasing a turn-off current commutating rate of said gate turn-off thyristor by increasing a breakdown voltage of said diode.  
     
     
       13. The method of  claim 12 , further comprising: 
       maintaining a unity turn-off gain of said circuit until a turn-off transient process.  
     
     
       14. The method of  claim 12 , further comprising: 
       selecting said turn-off voltage V OFF  to satisfy the following relation: BV E +BV GC >V OFF , wherein BV E  is the breakdown voltage of said diode and BV GC  is a gate-to-cathode breakdown voltage.  
     
     
       15. The method of  claim 12 , further comprising: 
       setting the breakdown voltage of said diode BV E  to be less than said turn-off voltage V OFF , so that a sum of a gate-to-cathode breakdown voltage BV GC /2 and the breakdown voltage of said diode BV E  is less than said turn-off voltage V OFF .  
     
     
       16. The method of  claim 12 , further comprising: 
       setting a turn-off voltage V OFF  of said voltage source to a level where current through an internal diode of the gate turn-off thyristor D GC  does not flow forward once commutated.